Strip shared directory from mountinfo’s mount points with sandbox=chroot
When using sandbox=chroot, /proc/self/mountinfo
still contains the pre-chroot mount point paths. To open them, we need to strip the shared directory as a prefix from them.
This series does so by first canonicalizing the shared directory path, and then (when using sandbox=chroot) stripping it from every mount point in /proc/self/mountinfo
that we want to open.
(Reported by German)